This application is based on and incorporates herein by reference Japanese Patent Application Nos. Hei. 11-311466 filed on Nov. 1, 1999, Hei. 11-311467 filed on Nov. 1, 1999, and Hei. 11-311561 filed on Nov. 1, 1999.
1. Field of the Invention
The present invention relates to an intake air controller including throttle valve suitable for use in a vehicle.
2. Description of Related Art
JP-A-1-53027 discloses an intake air controller for a vehicle, which includes a throttle body containing a throttle valve and a throttle valve shaft. One end of the throttle valve shaft is supported through a ball bearing having inner and outer races. A ring-like bearing stop cover is inserted into a cylindrical bearing holder of the throttle body to prevent the ball bearing from sliding out.
However, in JP-A-1-53027, since the bearing stop cover is used to prevent the slide-out of the ball bearing, the numbers of parts and manufacturing steps are increased, thereby increasing the manufacturing cost. Further, since the bearing stop cover is installed, the axial length of the bearing holder is lengthened, thereby axially enlarging the throttle body. As a result, an installation performance of the throttle body into an engine compartment is worsened.
JP-B2-8-26789 discloses an intake air controller for a vehicle, which includes a throttle body containing a throttle valve and a throttle valve shaft, and throttle position sensor detecting a rotation angle of the throttle valve. One end of the throttle valve shaft is supported through a ball bearing having inner and outer races.
The outer race is press inserted into an inner surface of a bearing holder, and the throttle valve shaft is press inserted into the inner race to eliminate an internal thrust clearance of the ball bearing for improving the detecting accuracy of the throttle position sensor. The throttle valve and the throttle valve shaft are made of iron series metal, and the throttle body is made of aluminum die-cast.
When a vehicle is used under an extremely high temperature condition (for example, 120xc2x0 C.) or an extremely cold temperature condition (for example, xe2x88x9240xc2x0 C.), the throttle valve and the shaft expand more than the throttle body, i.e., the throttle body shrinks more than the throttle valve and the shaft due to a thermal expansion coefficient difference between the throttle valve including the shaft and the throttle body. Thus, when the throttle valve is firmly positioned in a bore forming an intake air passage for eliminating the internal thrust clearance, the outer periphery of the throttle valve contacts the bore at an idling position thereof where the throttle valve fully closes the intake air passage.
In a conventional intake air controller, a throttle valve is attached to a throttle valve shaft without adjusting a clearance between the shaft and a bearing portion, thereby increasing a shaft vibration. Thus, a clearance between the outer periphery of the throttle valve and the inner wall of the bore varies.
Further, in the conventional intake air controller, a throttle valve fully closes an intake air passage at a particular rotation angle with respect to a surface perpendicular to the axis of the intake air passage. The throttle valve is attached to the shaft by making the throttle valve directly contact the inner wall of the throttle body to position the center of the throttle valve at the center of the intake air passage.
This conventional attaching method cannot be applied to an intake air controller in which the throttle valve fully closes the intake air passage by zero degree rotation angle, i.e., the throttle valve fully closes the intake air passage perpendicularly to the intake air passage, for improving a fluid flow amount control at a low flow amount range.
A first object of the present invention is to reduce the numbers of parts and manufacturing steps for an intake air controller, thereby reducing the manufacturing cost thereof, and to compact a throttle body.
A second object of the present invention is to prevent a micro-contact between a throttle valve and a throttle body due to a thermal expansion coefficient difference therebetween.
A third object of the present invention is to suppress a clearance between the outer periphery of a butterfly valve used for a throttle valve and the inner wall of the fluid flow passage from changing, and further to make the clearance small.
According to a first aspect of the present invention, an axial end of a bearing holder is crimped to prevent a bearing from sliding out, so that a bearing stop cover in the prior art is not needed to stop the slide-out of the bearing.
Thus, the number of parts and manufacturing steps for the intake air controller are reduced, thereby reducing the manufacturing const thereof. Since the bearing stop cover is not needed, the axial length of a bearing holder of the throttle body is shortened, thereby axially compacting the throttle body. As a result, an installation performance of the throttle body into an engine compartment is improved.
According to a second aspect of the present invention, within a ball bearing, a total of an internal thrust clearance between an inner race and a ball and an internal thrust clearance between an outer race and the ball is set at a predetermined clearance amount.
Thus, a shaft can slide in the axial direction, so that the throttle valve escapes from contacting the inner wall of the throttle body. That is, the micro-contact between the throttle valve and the throttle body due to the thermal expansion coefficient difference therebetween is prevented.
According to a third aspect of the present invention, first and second adjusting instruments put and support a shaft therebetween to position the shaft at the center of the fluid flow passage.
Thus, the clearance between the outer periphery of the butterfly valve and the inner wall of the fluid flow passage is suppressed from changing, and is made small.